Caen VX1290A TDC adjustment

To achieve 25ps bin with 100ps clock, a signal is split into 4 different RC circuits. Value of C is adjustable with four 3-bit calibration constants. The goal is to have a change in a least-significant bit of time measurement for a random signal to occur with the same probability in all 4 channels.

A) A measurement of TDC bin size was done with a signal delayed by 200ns. Before adjustment, the bin size was measured to be 24.86ps. After adjustment, it became 25.11ps

B) Timing resolution was measured by the width of time difference between 2 signlas from TI unit. It was 39.5ps before and 35.1ps after adjustment. Similar measurement for F1TDC gave 49ps resolution.